The majority of the fastener driving tools in use today are pneumatically powered. Pneumatic tools use a source of pressurized air that is supplied to the tool through a hose. This is a severe limitation on the versatility of pneumatic tools; they must be tied to a source of air pressure by a hose, limiting the distance which the tools can be moved from the air source. In addition, some remote job sites make it difficult to provide an easily accessible and economical air source. The added expense of providing electrical service to power the air source, or using alternative power sources (such as gasoline powered compressors) for providing the compressed air, subtract from the efficiency and convenience that pneumatic tools traditionally provide. Therefore, there have been many attempts to provide alternatives to pneumatically actuated tools that can be used in situations where the pneumatic tools are not convenient.
One alternative that has been developed is a tool which uses electricity to provide the power needed to drive fasteners of the type and size that traditionally pneumatic tools drive. Most of these tools use an electric motor to power one or more flywheels which, in turn, store sufficient energy to drive the fasteners. Examples of these tools are set forth in U.S. Pat. Nos. 4,042,036; 4,121,745; 4,204,622; 4,298,072; 4,323,127; and 4,964,558. However, these tools still suffer from the same limitation as the pneumatic tools in that they must be connected by a cord to an energy source.
A second alternative which has recently been developed is a completely self-contained fastener driving tool which is powered by internal combustion of a gaseous fuel-air mixture. Examples of these tools are found in U.S. Pat. Nos. 2,898,893; 3,042,008; 3,213,608; 3,850,359; 4,075,850; 4,200,213; 4,218,888; 4,403,722; 4,415,110; and 4,739,916. While these tools need no connection to an external power source and are extremely versatile, they tend to be somewhat large, complex, heavy and awkward to use. In addition, they can be less economical to operate in that the fuel used is relatively expensive.
Another class of tools which is traditionally used as an alternative to pneumatic tools is the powder or propellant actuated tool. Powder or propellant actuated fastener driving tools are used most frequently for driving fasteners into hard surfaces such as concrete. The most common types of such tools are traditionally single fastener, single shot devices; that is, a single fasteners is manually inserted into the barrel of the tool, along with a single propellant charge. After the fastener is discharged, the tool must be manually reloaded with both a fastener and a propellant charge in order to be operated again. Examples of such tools are described in U.S. Pat. Nos. 4,830,254; 4,598,851; and 4,577,793.
In propellant actuated tools, there are many different type of cartridges used for propellants. For examples, U.S. Pat. No. 3,372,643 teaches a low explosive primerless charge consisting of a substantially resilient fibrous nitrocellulose pellet with an igniter portion and having a web thickness less than any other dimension of the pellet. U.S. Pat. No. 3,529,548 is directed to a powder cartridge consisting of a cartridge case constructed of two separate pieces which contain a central primer receiving chamber and an annular propellant receiving chamber. U.S. Pat. No. 3,911,825 discloses a propellant charge having an H-shaped cross section composed of a primer igniter charge surrounded by an annular propellant powder charge.
A second type of powder actuated tool has also been used in recent times. This tool still uses fasteners which are individually loaded into the firing chamber of the device. However, the propellant charges used to provide the energy needed to drive the fasteners are provided on a flexible band of serially arranged cartridges which are fed one-by-one into the combustion chamber of the tool. Examples of this type of tool are taught in U.S. Pat. No. 4,687,126; 4,655,380; and 4,804,127. In the tools heretofore mentioned, which use a cartridge strip assembly, there are a variety of strips which are available for use. U.S. Pat. No. 3,611,870 is directed to a plastic strip in which a series of explosive charges are located in recesses in the strip with a press fit. U.S. Pat. No. 3,625,153 teaches a cartridge strip for use with a powder actuated tool which is windable into a roll about an axis which is substantially parallel to the surface portion of the strip and having the propellant cartridges disposed substantially perpendicular to the surface portion. U.S. Pat. No. 3,625,154 teaches a flexible cartridge strip with recesses for holding propellant charges, wherein the thickness of the strip corresponds to the length of the charge contained therein. U.S. Pat. No. 4,056,062 discloses a strip for carrying a caseless charge wherein the charge is held in the space by a recess and a tower-shaped wall and is disposed in surface contact with the annular surface within the cartridge recess. U.S. Pat. No. 4,819,562 describes a propellant containing device which has a plurality of hollow members closed at one end and a plurality of closure means each having a peripheral rim which fits into the open end of the hollow members of the device.
Recently, several powder actuated tools have been developed which operate in a manner similar to the traditional pneumatic tools; that is, these devices contain a magazine which automatically feeds a plurality of fasteners serially to the drive chamber of the tool, while a strip of propellant charges is supplied serially to the tool to drive the fasteners.
One example of such a tool is described in U.S. Pat. No. 4,821,938. This patent, which teaches an improved version of a tool taught in U.S. Pat. No. 4,655,380, is directed to a powder actuated tool with an improved safety interlock which permits a cartridge to be fired only when a safety rod is forced into the barrel and cylinder assembly and when the barrel and cylinder assembly has been forced rearwardly into its rearward position.
Another example of this type of tool is taught in U.S. Pat. No. 4,858,811. This tool, which is an improved version of the tool taught in U.S. Pat. No. 4,687,126, incorporates a handle, a tubular chamber, a piston, and a combustion chamber within the tubular chamber, the combustion chamber receiving a cartridge in preparation for firing, which upon ignition, propels the piston forwardly for the driving of a nail. A fastener housing is located forwardly of the tubular chamber, and is provided for directing a strip of fasteners held by a magazine upwardly through the tool during repeated tool usage.
Both of the aforementioned recent powder actuated tools, however, are designed to drive fasteners into hard surfaces such as concrete. Consequently, a need exists for a propellant actuated tool that can be efficiently used as a replacement for traditional pneumatic tools which drive fasteners into wood.
It is thus an object of the present invention to overcome the disadvantages of the prior art by providing a propellant actuated .fastener driving tool which is lighter, less complex, and very similar to the traditional pneumatic tool.
It is also an object of the present invention to provide a tool which can be easily and efficiently used in those work environments where pneumatic tools are traditionally used.
It is further an object of the present invention to provide a self-contained fastener driving tool which is safer and less expensive to operate than tools currently available and known in the art.
Additional objects, advantages, and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.